AVD connecton error

Take this:

1. Investigate the Root Cause

• Event Logs: Check the Windows Event Viewer on the affected session hosts for errors related to RDP, Azure agents, or network connectivity.
• Azure Monitor: Use Azure Monitor to review metrics and logs for the session hosts. Look for anomalies in CPU, memory, or network usage.
• Agent Logs: Review the logs for the Azure Virtual Desktop agent and RDP agent. These logs can provide insights into why the agents are becoming unhealthy.

2. Common Causes

• Update Compatibility: The March CU update (KB5053657) might have introduced compatibility issues with the AVD agents or network settings.
• Network Configuration: Ensure that the affected session hosts are correctly configured within the virtual network (VNet). Verify that DNS settings and firewall rules allow communication between the hosts and Azure services.
• Agent Health: Unhealthy agents can result from corrupted installations or missing dependencies. Reinstalling the agents, as you've done, is a valid workaround.

3. Troubleshooting Steps

• Reinstall Agents: If reinstalling the agents resolves the issue temporarily, consider automating this process using PowerShell or Azure Automation.
• Deallocate and Redeploy: Deallocating and redeploying the affected session hosts can reset their state and resolve connectivity issues.
• Rollback Updates: If the issue persists, consider rolling back the March CU update on all session hosts until a permanent fix is identified.